A malocclusion is a misalignment of teeth or incorrect relation between the teeth of the two dental arches. The term was coined by Edward Angle, the “father of modern orthodontics,” as a derivative of occlusion, which refers to the way opposing teeth meet. Angle based his classifications of malocclusions on the relative position of the maxillary first molar. According to Angle, the mesiobuccal cusp of the upper first molar should align with the buccal groove of the mandibular first molar. The teeth should all fit on a line of occlusion, which is a smooth curve through the central fossae and cingulum of the upper canines, and through the buccal cusp and incisal edges of the mandible. Any variations therefrom result in malocclusion.
There are three classes of malocclusions—Class I, II, and III. Further, class II is subdivided into three subtypes:
Class I: Neutrocclusion In Class I the molar relationship of the occlusion is normal or as described for the maxillary first molar, but the other teeth have problems like spacing, crowding, over or under eruption, etc.
Class II: Distocclusion (retrognathism, overjet) In this situation, the upper molars are placed not in the mesiobuccal groove, but anteriorly to it. Usually the mesiobuccal cusp rests in between the first mandibular molars and second premolars. There are two subtypes:
Class II Division 1: The molar relationships are like that of Class II and the anterior teeth are protruded.
Class II Division 2: The molar relationships are class II but the central incisors are retroclined and the lateral incisors are seen overlapping the central incisors.
Class III: Mesiocclusion (prognathism, negative overjet) In class III malocclusions the upper molars are placed not in the mesiobuccal groove, but posteriorly to it. The mesiobuccal cusp of the maxillary first molar lies posteriorly to the mesiobuccal groove of the mandibular first molar. This malocclusion is usually seen when the lower front teeth are more prominent than the upper front teeth. In such cases, the patient very often has either a large mandible or a short maxillary bone.
Orthodontics, formerly orthodontia (from Greek orthos “straight or proper or perfect”; and odous “tooth”), is the first specialty of dentistry that is concerned with the study and treatment of malocclusion (improper or dysfunctional bite), which may be a result of tooth irregularity, disproportionate facial skeleton relationship, or both. Orthodontics treats malocclusion through the displacement of teeth via bony remodeling and control and modification of facial growth.
This process has been traditionally accomplished by using static mechanical forces to induce bone remodeling, thereby enabling teeth to move. This widely accepted approach to treating malocclusion takes about twenty-four months on average to complete, and the time cannot be shortened by increasing the force, due to the pain and risk of root resorption with excess force. In this approach, orthodontic braces consist of an archwire that applies a continuous static force to the dentition and interfaces with brackets that are affixed to each tooth. Such braces are used to treat a number of different classifications of clinical malocclusion. These clinical malocclusions include underbites, overbites, cross bites, open bites, and crooked teeth, for both aesthetic and functional/structural reasons.
Orthodontic treatment is complicated by the fact that it is uncomfortable and/or painful for patients, and the orthodontic appliances are perceived as unaesthetic, all of which creates resistance to use. Further, the 24-month treatment time is very long, and further reduces usage and compliance, which can include chronic poor dental hygiene. In fact, some estimates provide that less than half of the patients who could benefit from such treatment elect to pursue orthodontics.
Kesling introduced the tooth-positioning appliance in 1945 as a method of refining the final stage of orthodontic finishing after debanding. A positioner was a one-piece pliable rubber appliance fabricated on the idealized wax set-ups for patients whose basic treatment was complete. Kesling also predicted that certain major tooth movements could also be accomplished with a series of positioners fabricated from sequential tooth movements on the set-up as the treatment progressed. However, this idea did not become practical until the advent of 3D scanning and computer modeling in 1997.
Removable clear appliances, such as the Invisalign® system, have been introduced for treating malocclusion, and provide greatly improved aesthetics since the devices are transparent. However, because these appliances can be removed, compliance can be an issue, and failure to use at least 22 hours a day slows the overall treatment time.
As a treatment modality, aligners are also limited in the classifications of clinical malocclusion that they can address. In the past, aligners have not been able to easily rotate or extrude teeth because the aligner cannot adequately direct force in all directions. Conditions that can be difficult to treat with an Invisalign® appliance or are contra-indicated altogether include:                crowding and spacing over 5 mm        skeletal anterior-posterior discrepancies of more than 2 mm (as measured by discrepancies in cuspid relationships)        centric-relation and centric-occlusion discrepancies        severely rotated teeth (more than 20 degrees)        open bites (anterior and posterior) that need to be closed        extrusion of teeth        severely tipped teeth (more than 45 degrees)        teeth with short clinical crowns        arches with multiple missing teeth.        
Being aware of these limitations, Align Technologies has recently combined the Invisalign® clear aligners with clear attachments that adhere to teeth and can provide a surface on which force can be exerted in any desired direction. A custom mold is made using a 3D model of the patients teeth with pockets therein for the placement of a force attachment, the placement and shape of which are determined using proprietary modeling software. The relevant force attachments are made and fitted into the mold, adhesive applied to the attachments, and the mold applied to the teeth. This allows precise and quick placement of the clear attachments, which are then affixed using light cure. There is some affect on aesthetics, but because the force attachments are also clear, they are not very noticeable from a distance.
In addition to static forces, cyclic or pulsed forces (e.g., vibration) can also be used for orthodontic remodeling. Kopher and Mao assessed cyclic forces of 5 Newtons peak magnitude at 1 Hz in rabbits, while Peptan and Mao assessed cyclic forces of 1 N at 8 Hz in rabbits, and Vij and Mao assessed cyclic forces of 300 mN at 4 Hz in rats. In aggregate, the data from these three studies indicated that cyclic forces between 1 Hz and 8 Hz, with forces ranging from 0.3 N to 5 N, increased bone remodeling. Rates depended on different methodologies, but increases of 2.5× with vibrational forces were common. Since Dr. Mao's experiments, an independent study out of Japan has confirmed and strengthened the idea of vibration at 60 Hz for speeding orthodontic tooth movement, and an earlier 50 Hz study in Russia also confirms the basic premise. In fact, by now there is a well-established literature confirming the efficacy of this treatment modality.
The early Mao studies provided a basis for both possible efficacy and likely safety for using vibration in humans to assist orthodontic tooth movement. However, the original force (5 Newton) and devices were completely unsuitable for human use, and it was unclear that rabbit cranial results would be applicable to human dentition. Thus, considerable additional effort was needed to translate the promising results into a human suitable, commercially successful device.
OrthoAccel® Technologies Inc., invented and clinically tested the first commercially successful orthodontic vibrating device, as described in US2008227046, designed to apply cyclic forces to the dentition for accelerated remodeling purposes. Both intra-oral and extra-oral embodiments are described in US2008227046, each having processors to capture and transmit patient usage information. The bite plate was specially designed to contact occlusal as well as lingual and/or facial surfaces of the dentition, and thus was more effective than any prior art devices in conveying vibrational forces to the teeth.
Further, the device has actually been tested in a double blind clinical trial and has been shown to speed orthodontic remodeling as much as 50%. As such it is truly a breakthrough in orthodontic technology (Kau 2010, see also clinicaltrials.gov). Finally, the device is slim, capable of hands free operation, lacks the bulky headgear of the prior art devices, and has optimized force and frequency for orthodontic remodeling. Thus, its comfort level and compliance was also found to be high, with patients reporting that they liked the device, especially after the motor was redesigned to be quieter and smoother, as described in US2010055634 et seq. In fact, this device has been marketed as AcceleDent® in Australia, the United Kingdom, Europe, China, South Korea, Japan, Kenya, and the United States and has achieved remarkable commercial success since its recent introduction (2009). AcceleDent® represents the first successful clinical approach to accelerate orthodontic tooth movement by modulating bone biology in a non-invasive and non-pharmacological manner.
However, further improvements in the above device are always beneficial, and this application addresses some of those improvements.